The invention refers to a method of bonding roofbolt rods to boltholes.
It is a common practice to use unsaturated polyester resins and polyurethanes as reactive resin mass for bonding boltrods in boltholes. For this purpose, the two components polyisocyanate and polyol which form the polyurethane are filled separately in two compartments of a cartridge which may consist e.g. either of a synthetic foil or an extruded brittle mass (please refer to DE-PS No. 26 41 776). When introducing the bolt into the bolthole by a rotating movement, the compartments will be destroyed, so that the two components mix and react, forming polyurethanes. According to DE-AS No. 12 05 038 and DE-AS No. 17 84 458, the polyurethane resin will gel no earlier than after 2 hours and harden after 5 to 6 hours. For practical reasons, however, much shorter gelling and hardening times are required, since the bolt rod in upwardly oriented boltholes must be secured against sliding prior to attaining the gelling point and the roofbolt, particularly in tunneling and mining applications, must as early as possible attain load-bearing properties.
In the disclosure of DE-AS No. 27 05 751 there is described a system avoiding such drawback, by using polyols containing tertiary amino groups as hydroxyl components, which at the same time act as catalysts, so that gelling and hardening durations of less than 1 minute are achieved. According to claim 3 of the above disclosure, however, the admixture of water is limited to 0.5% by weight, related to polyol. In the case of more substantial water volumes, e.g. in damp boreholes, the mix will foam so much that the ultimately hardened foam is not capable of sustaining any sizable tractive forces.
A copending application Ser. No. 454,479 filed by the same inventor on Dec. 29, 1982 also discloses a method of bonding roofbolt rods to boltholes.